242 
fxus66 keka 211212 
afdeka 


Area forecast discussion 
National Weather Service Eureka California 
410 am PST Friday Nov 21 2008 


Synopsis...weak high pressure will bring fair skies today...except 
for morning fog in the northern interior valleys. A trough moving 
through the Pacific northwest will bring a chance of rain tonight. 
Dry conditions are expected Saturday evening through Sunday night. 


&& 


Short term...today through Monday night...a weak transient ridge 
will move through the Pacific northwest today and provide clear 
skies today...with the exception of morning fog in the interior 
valleys north of Cape Mendocino. However...clouds will begin 
increasing this evening in advance of an upper trough and weak cold 
front approaching the Pacific northwest. The best rainfall chances 
from this system will be north of the cape tonight. Showers will 
taper off quickly Saturday morning as the trough moves east. Models 
show ridging building over the West Coast by 12z Sunday...and Sunday 
will be a fair day across the area following patchy fog in the 
morning. Clouds will be increasing Monday as low pressure aloft 
approaches the West Coast. Model agreement is not very good 
regarding the strength of the trough...and will maintain a slight 
chance of rain Monday with probability of precipitation increasing Monday night. Kl 


Previous long term...Tuesday through Thursday...long term forecast 
continues to be rather uncertain in the details beyond Monday. 
Models are showing an upper low closing off somewhere around 35n 
125w...and then moving somewhere into the California coast in the 
Tuesday-Thursday timeframe. Model performance with cut off lows tends to 
be poor...especially 4 to 6 days out...which means holding off on 
putting any confidence in a single model or model run. Have made 
little changes to this period other than to keep probability of precipitation well into the 
chance category...which is the climatological value for middle to late 
Nov. Northwest California looks to be affected in some way by this system 
middle and late week...though the exact details of when and how will 
likely remain uncertain for several more days. Alm 


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Aviation...VFR conditions most areas though fog satellite product 
shows LIFR fog developing in Trinity and Eel River valleys and 
patchy fog in other valleys. This fog should dissipate by late 
morning with clear skies for rest of afternoon. Next front to come 
through early Sat morning. Models show sharp edge of clouds to move 
in starting in far northwest near cec after about 9pm. With increasing 
clouds there should be less fog in the valleys Friday night but MVFR 
ceilings developing in light rain near cec and acv after midnight. Dean 


&& 


Marine...seas still running near 11-13 feet and latest run of enp 
forecasts them to peak early this morning. They will briefly 
subsided tonight before next swell train associated with low in 
eastern Pacific moves in on Saturday. Northwest pressure gradient 
still producing northwest 25kt winds per laps in southern end of outer 
waters and have issued Small Craft Advisory. These winds will decrease this afternoon 
as next surface trough and associated front approaches. The front 
passes through the far northwest corner about 1am early Saturday morning 
and whats left of it through the southern waters by midmorning. 
Surface high then builds with northerly winds developing but look to 
stay below small craft criteria. Extended forecast for next week in 
question as models inconsistent. Next trough for Monday splits and 
HPC has southern surface low developing well off of sfo and then it 
drifts southeast to off the la bight by Thursday. Meanwhile the northern 
portion has the surface trough and associated front not passing 
through until Tuesday night. 00z GFS had developed very strong low 
in Gulf of Alaska Tuesday that developed swell which translated into 
our coastal waters as 15-17 feet seas Wednesday night. These look overdone 
and have backed off on the forecast to 10-12 feet. Dean 


&& 


Eka watches/warnings/advisories... 


Small Craft Advisory for hazardous seas through Saturday evening for 
pzz450-455-470-475. 


Small Craft Advisory for winds through 2 PM PST this afternoon for 
pzz475. 


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